Citation

Poreh M, Morgan HP. Fire Safety J. 1996; 27(2): 159-178.

Copyright

(Copyright © 1996, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

A general, dimensionally homogeneous power law for describing the vertical variation of the mass flux M within limited regions in the near field of fire-generated turbulent flames and plumes is derived. The derivation assumes that M(z) is determined by the geometric size of the fire--D, the buoyancy flux generated by the heat flux of the fire--B, and the total mass flux of fresh air required for stoichiometric combustion of fuel--Ms, which implies that, in general, the variation of M depends on a dimensionless number N, which is approximately proportional to Q2/D5, where Q is the heat flux of the fire. Simpler forms of this general law are then derived for the asymptotic cases of small and large values of N and for geometrically similar fires whose heat output Q is determined by D and Ms, which are shown to satisfy the condition N = constant. The required dimensionless specification of regions where such laws may be valid is also derived. Previously suggested power laws, some of which appear to be contradictory to each other, are then examined. Only two of them have been found to be incompatible with the derived power laws. The remainder are found to be of the simpler forms derived for small, large and constant values of N.